1. Field of the Invention
This invention generally relates to an electric derailleur motor unit for an electric bicycle derailleur. More specifically, the present invention relates to calibrating a motor that moves a derailleur.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. In particular, the bicycle transmission has been significantly changed over the years.
Derailleur operated bicycle transmissions typically comprise a plurality of sprockets that rotate with another rotating member (e.g., the front crank and/or the rear wheel of the bicycle) and a derailleur that is used to shift a chain among the plurality of sprockets. Conventional derailleur transmissions were manually controlled by a hand operated actuator such as a lever or twist-grip attached to the bicycle handlebar, wherein the derailleur is connected to the actuator by a Bowden cable.
Recently, bicycles have been equipped with electrical components to make riding easier and more enjoyable for the rider. Some bicycles are equipped with automatic shifting units that are automatically adjusted according to the riding conditions by a cycle computer or control unit. In particular, the front and rear derailleurs have recently been automated. Recently, various electronic devices have been used to determine one or more operating parameters of the derailleur. Such parameters may be used for informational purposes or for electronically controlling the derailleur. A common operating parameter is the position of the derailleur relative to the plurality of sprockets. In the past, potentiometers that cooperated with various moving components of the derailleur were used to ascertain the position of the derailleur. Since derailleurs usually have a relatively small range of motion, high precision potentiometers were required for this purpose. That was especially true when the information provided by the potentiometer is used by an electronic device to shift the chain among the plurality of sprockets. Unfortunately, high precision potentiometers are relatively expensive, thus making electronically controlled derailleurs using high precision potentiometers unsuitable for mass production. Inexpensive potentiometers have nonlinear characteristics, and such characteristics vary from one potentiometer to another. Thus, the actual derailleur position is difficult to ascertain with such potentiometers, and the unpredictability from one potentiometer to another also makes derailleurs using such potentiometers unsuitable for mass production.
Generally speaking, the front derailleur is typically secured to the seat tube of the bicycle frame or the bottom bracket. Basically, a front derailleur includes a fixed or base member non-movably secured to a bicycle frame, and a movable member supported to be movable relative to the fixed member. Typically, the fixed member is a tubular clamping member that is secured to the seat tube. The movable member typically has a chain guide with a pair of cage plates for contacting and moving a chain between the front sprockets. The movable member is usually biased in a given direction relative to the fixed member by a spring. The movable member is usually moved relative to the fixed member by pulling and/or releasing a shift control cable that is coupled to the front derailleur. The movable member and the fixed member usually are interconnected through pivotal links. In a motorized front derailleur, the motor is used to pull and release a control cable or the motor is connected by a drive train to the front derailleur.
It will be apparent to those skilled in the art from this disclosure that there exists a need for an improved electric bicycle derailleur. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.